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### Quantum Physics Homework

**Photoelectric Effect**

- The threshold frequency of tin is 1.2 x 10
^{15}Hz. What is the threshold wavelength?
What is the work function of tin? Ans: 250 nm; 4.97 eV
- In number one, if 167 nm light falls on tin, what is the kinetic energy of ejected photoelectrons?
Ans: 2.47 eV
- In number one, what is the speed of the ejected photoelectrons? Ans: 9.31 x 10
^{5} m/s
- The threshold frequency of a given metal is 6.7 x 10
^{14}Hz. It is illuminated by 350 nm
light. What is the kinetic energy of the ejected photoelectrons? Ans: 0.78 eV
- In number four, the metal is illuminated by 550 nm light. What is the kinetic energy of the ejected photoelectrons? Ans: 0 eV
- The work function of iron is 4.7 eV. What is the threshold wavelength of iron? Ans: 264 nm
- If the iron is exposed to 150 nm light, what is the kinetic energy of the ejected electrons? Use work function of iron given in number 6. Ans: 3.58 eV
- In number 7, what is their speed? Ans: 1.12 x 10
^{6}m/s

**de Broglie Wavelength**

- What is the de Broglie wavelength of a deuteron of mass 3.3 x 10
^{-27}kg that moves with a speed of 2.5 x 10^{4}m/s. Ans: 8.03 x 10^{-12}m
- What is the de Broglie wavelength of a proton (mass=1.67 x 10
^{-27}kg) moving at 1 x 10^{6}m/s? Ans: 3.97 x 10^{-13}m
- An electron is accelerated across a potential difference of 54 V. Find the maximum velocity of the
electron. Ans: 4.36 x 10
^{6}m/s
- What is the de Broglie wavelength of the electron in number three? Ans: 1.67 x 10
^{-10}m
- The kinetic energy of an electron is 13.65 eV. Find the velocity of the electron. Calculate its de Broglie wavelength. Ans: 2.19 x 10
^{6}m/s; 0.332 nm
- An electron has a de Broglie wavelength of 400 nm. What is its velocity? Ans: 1,818 m/s

**Atomic Models**

- An electron in a mercury atom drops from 8.82 eV to 6.67 eV above its ground state. What is the energy of the photon emitted? What is its frequency? Ans: 2.15 eV; 5.19 x 10
^{14}Hz
- What energy is associated with the second, third, fourth, fifth, and sixth energy levels in the hydrogen
atom? Ans: -3.4 eV; -1.51 eV; -0.85 eV; -0.54 eV; -0.38 eV
- Using the values calculated in number 2, determine the following energy differences for the hydrogen
atom: E
_{6} - E_{5} and E_{5} - E_{3}. Ans: 0.16 eV; 0.97 eV
- Using the values calculated in number three, determine the frequencies of light emitted by the photon given off in the energy changes.
Ans: 3.86 x 10
^{13}Hz; 2.34 x 10^{14}Hz
- Determine the wavelengths of the emitted photons in number four. Ans: 7772 nm; 1282 nm

Quantum Physics Notes

Quantum Physics Sample Problems